<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    
    <input type="button" value="显示图片" id="btn">
    <img src="" alt="" id="im">
    <script>
       var btnObj= document.getElementById("btn");
       btnObj.onclick=function(){
            var imObj=document.getElementById("im");
            imObj.src="images/1.jpg";
            imObj.width="400";
            imObj.height="300";


        }

    </script>
</body>
</html>